Low Voltage Lock Out ?

[DaveH]

Hey Guys,
2001 Mercury Optimax 225 serial #0T272917 290 hours
Having issues of no start and long continuous horn. ECM shows no power on the DDT scan tool my mechanic has.
When the key is turned on there no horn sound and after about 15 seconds a continuous horn, motor cranks but won't start.
There power going to the fuel pumps but it stops about every ten seconds then power again.
There's a you tube video of the same issue but I'm trying to figure out how to link it in.

The morning it quit on me I had launched in foggy conditions and was using nav lights and running at 5mph and the gps.
I had the battery on a 2amp maintainer charger the night before and I believe the battery was running at about 12.2 volts when the motor just died
and wouldn't start and then the horn came on with the key on, so I got towed in.
I've got a appointment with a shop to put it on a laptop to see what it will tell us, the ddt scanner wouldn't read anything because i was told it gets power from the ecm.
So I went out and bought a new odyssey M2150 and shelved the sam's club grp 31, Im hoping the motor went into a safe mode and just needs reset.
So any idea's what is causing this will be appreciated. Thanks

[Savage]

Test the Main Power Relay.

[DaveH]

The mechanic today can’t get any reading, the pcm has no power to it. Scanned with the laptop and ddt scan tool.

[Savage]

Did he test the Main Power Relay as suggested?

[DaveH]

Did he test the Main Power Relay as suggested?

Yes he replaced with a new one they had in stock.

[Savage]

Did his testing determine that the MPR was defective?

[DaveH]

Did his testing determine that the MPR was defective?

The new mpr gave the same results as the the original, the ecm wouldn't register on the ddt and the lap top program. He said that the ecm is at fault.
There was another optimax at the shop but he wasn't able to pull that one and test.
I'm still going to try swapping one out and see if that does anything before I send this one off.

[lpugh]

The new mpr gave the same results as the the original, the ecm wouldn't register on the ddt and the lap top program. He said that the ecm is at fault.
There was another optimax at the shop but he wasn't able to pull that one and test.
I'm still going to try swapping one out and see if that does anything before I send this one off.

ECM would be the least likely failure I think
Testing is required, guessing gets expensive, a good tech should be able in most cases to pin that problem down in a hour or less

[DaveH]

ECM would be the least likely failure I think
Testing is required, guessing gets expensive, a good tech should be able in most cases to pin that problem down in a hour or less

My confidence level in the shop isn’t high seems all He wanted to do was try the simplest thing hook up his scan tools and plug a new mpr in it and not do much further and tell me the pcm is bad.
The guy in the you tube video said that’s what he had to get to fix his issue, replace the pcm.

[lpugh]

Never replace a ECM without checking all power/circuits. Even then if the ECM has failed there is a risk of another failure when connected if the cause of failure has no been identified. This could be as simple as a key switch or connection problem, Power point, loose ground on the block
Keep in mind what Savage said TEST, did not say replace as that is a poor substitute for testing
Does North Hollywood Marine still operate in your area, Been years, but they used to have top notch techs
Do you have any experience at all with electrical testing and have a quality DVOM
Would not be difficult to talk an experienced tech thru this to pin down the cause, I am not a Mercury tech (automotive) but I am sure with the electrical diagram in front me, I could find the answer in an hour or less
Think need to find a, Mo better technician, Maybe Don, Savage or Joe could offer some ideas on locating one in you area

[DaveH]

No they don’t. The mechanic who I first took it to used to work there and Castaic Marine, he works on boat on a part time basis and has a full time job as a HD mech. he went though the system first and got to the point where the ddt he has would show no power to the pcm and would not read it.
it was his suggestion to have it looked at lakeside marine and hooked up to there laptop.
so I did.
His scan tools showed the same, no pcm found.
he also installed a new MPR and that didn’t do anything.
I thinking I could swap my pcm on someone’s optimax and see if it demonstrates the same issue.
I don’t want to use there pcm on mine and possible fry it.
Ive contacted Simonperftech and plan on sending the pcm to him and see what’s up with the pcm.
The only other place to take the boat to would be Anglers Marine in Anaheim and cash in my 401k.

[DaveH]

Well got the pcm back from Simon perftech and I'm headed out to reinstall and will be happy camper if all works as it should.
They just said the pcm was bad, no detail on what part of it fried, 19 year old pcm so things go bad, I still think using a less than required battery and letting the voltage drop down due to running in the fog had something to do with it.
Fast turn around, 3 days from mail box to mail box. Dawn at Simon is awesome !

[lpugh]

Would be wise to ask Eric if it the actuators, harness or high voltage could have been the cause of failure, would be a bummer to have a repeat. If unknown a lot of testing needs to be done before connecting the new unit.
Eric may know what circuits need testing if any, in most cases PCM failures are caused by an outside source such as short circuits or very high voltage

[DaveH]

Would be wise to ask Eric if it the actuators, harness or high voltage could have been the cause of failure, would be a bummer to have a repeat. If unknown a lot of testing needs to be done before connecting the new unit.
Eric may know what circuits need testing if any, in most cases PCM failures are caused by an outside source such as short circuits or very high voltage

Yes going to try and find out, I asked, but just got a invoice for repaired pcm.
Ran it on the hose so far so good.

[Savage]

I have seen improper troubleshooting techniques take out an otherwise good PCM also.

[DaveH]

I have seen improper troubleshooting techniques take out an otherwise good PCM also.

Going to hold off running it at the lake until I get some king of report from Simon's.

[EuropeanAM]

I have seen improper troubleshooting techniques take out an otherwise good PCM also.

+1

Have also seen some cases of loose battery cables/connections, faulty battery and (of course) lightening.